 /*******************************************************************************
  * Copyright (c) 2000, 2006 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  * IBM Corporation - initial API and implementation
  *******************************************************************************/
 package org.eclipse.ui;

 import org.eclipse.jface.viewers.ISelection;

 /**
  * A selection service tracks the selection within an object.
  * <p>
  * A listener that wants to be notified when the selection becomes
  * <code>null</code> must implement the <code>INullSelectionListener</code>
  * interface.
  * </p>
  * <p>
  * This interface is not intended to be implemented by clients.
  * </p>
  * @see org.eclipse.ui.ISelectionListener
  * @see org.eclipse.ui.INullSelectionListener
  */
 public interface ISelectionService {
     /**
      * Adds the given selection listener.
      * Has no effect if an identical listener is already registered.
      *
      * @param listener a selection listener
      */
     public void addSelectionListener(ISelectionListener listener);

     /**
      * Adds a part-specific selection listener which is notified when selection changes
      * in the part with the given id. This is independent of part activation - the part
      * need not be active for notification to be sent.
      * <p>
      * When the part is created, the listener is passed the part's initial selection.
      * When the part is disposed, the listener is passed a <code>null</code> selection,
      * but only if the listener implements <code>INullSelectionListener</code>.
      * </p>
      * <p>
      * Note: This will not correctly track editor parts as each editor does
      * not have a unique partId.
      * </p>
      *
      * @param partId the id of the part to track
      * @param listener a selection listener
      * @since 2.0
      */
     public void addSelectionListener(String partId, ISelectionListener listener);

     /**
      * Adds the given post selection listener.It is equivalent to selection
      * changed if the selection was triggered by the mouse but it has a
      * delay if the selection is triggered by the keyboard arrows.
      * Has no effect if an identical listener is already registered.
      *
      * Note: Works only for StructuredViewer(s).
      *
      * @param listener a selection listener
      */
     public void addPostSelectionListener(ISelectionListener listener);

     /**
      * Adds a part-specific selection listener which is notified when selection changes
      * in the part with the given id. This is independent of part activation - the part
      * need not be active for notification to be sent.
      * <p>
      * When the part is created, the listener is passed the part's initial selection.
      * When the part is disposed, the listener is passed a <code>null</code> selection,
      * but only if the listener implements <code>INullSelectionListener</code>.
      * </p>
      * <p>
      * Note: This will not correctly track editor parts as each editor does
      * not have a unique partId.
      * </p>
      *
      * @param partId the id of the part to track
      * @param listener a selection listener
      * @since 2.0
      */
     public void addPostSelectionListener(String partId,
             ISelectionListener listener);

     /**
      * Returns the current selection in the active part. If the selection in the
      * active part is <em>undefined</em> (the active part has no selection provider)
      * the result will be <code>null</code>.
      *
      * @return the current selection, or <code>null</code> if undefined
      */
     public ISelection getSelection();

     /**
      * Returns the current selection in the part with the given id. If the part is not open,
      * or if the selection in the active part is <em>undefined</em> (the active part has no selection provider)
      * the result will be <code>null</code>.
      *
      * @param partId the id of the part
      * @return the current selection, or <code>null</code> if undefined
      * @since 2.0
      */
     public ISelection getSelection(String partId);

     /**
      * Removes the given selection listener.
      * Has no effect if an identical listener is not registered.
      *
      * @param listener a selection listener
      */
     public void removeSelectionListener(ISelectionListener listener);

     /**
      * Removes the given part-specific selection listener.
      * Has no effect if an identical listener is not registered for the given part id.
      *
      * @param partId the id of the part to track
      * @param listener a selection listener
      * @since 2.0
      */
     public void removeSelectionListener(String partId,
             ISelectionListener listener);

     /**
      * Removes the given post selection listener.
      * Has no effect if an identical listener is not registered.
      *
      * @param listener a selection listener
      */
     public void removePostSelectionListener(ISelectionListener listener);

     /**
      * Removes the given part-specific post selection listener.
      * Has no effect if an identical listener is not registered for the given part id.
      *
      * @param partId the id of the part to track
      * @param listener a selection listener
      * @since 2.0
      */
     public void removePostSelectionListener(String partId,
             ISelectionListener listener);
 }

